The world's most popular sporting event kicks off today in Sao Paulo when Brazil, the tournament's host, takes on Croatia in the opening game at 5 p.m. local time.

Much of the attention ahead of the 2014 FIFA World Cup is focused on whether Brazil can pull off a successful tournament. The run-up has been plagued by strikes, controversies and unrest. Some of that was on display at a protest witnessed today by NPR's Lourdes Garcia-Navarro in Sao Paulo.

"Things got very ugly, very quickly," she tells our Newscast unit.

Police fired tear gas against a few dozen protesters, who were demonstrating against the World Cup.

"Clearly, the police, the security services want these protests to be contained very quickly," she says. "They don't want the narrative of the World Cup to be about these protests and take away from what's happening on the pitch."

Earlier, transit workers in Sao Paulo voted against resuming their strike for higher wages. Those arriving in Rio de Janeiro for the tournament won't be as lucky: Airport workers there have declared a 24-hour strike.

"They waited until the last minute, but the metro workers union has said it will be business as usual on the subway in Brazil's biggest city for the opening game of the World Cup. Most of the fans getting to the World Cup opener are arriving by metro, and Brazil's government had been hoping to avoid a shutdown. A five-day subway strike last week caused traffic chaos and left fans stuck in miles-long traffic jams. Still, while the labor action has been averted, protests are underway across the country. Demonstrators say they are upset over the cost of the tournament, which has been at the expense, they say, of investment in health and education."

But as NPR's Russell Lewis reports from Sao Paulo, many fans are ready for the games to start. He tells our Newscast unit that hundreds of people crowded outside the stadium to celebrate on Wednesday.

"Blowing horns, donning team jerseys and wearing wildly colorful hats, fans from many of the 32 countries playing in the World Cup were everywhere," he says. "Security was tight. Police were milling around as protective barriers were installed along the stadium's roads. Military and police helicopters circled overhead keeping an eye on the final preparations leading up to the opener as Brazil takes on Croatia."